Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2017	Jan. 31, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	EMCORE CORP
Entity Central Index Key	0000808326
Document Type	10-Q
Document Period End Date	Dec. 31, 2017
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2018
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Amendment Flag	false
Entity Common Stock, Shares Outstanding		27,199,762
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes